ok. Let me answer my own question. I walked it last week.
I was unable to find much details beforehand but the albergues in Ponvedra have some more. The detour is well marked; you cannot miss it. You can have a look at my pictures i uploaded here somewhere. The first stage is very nice, only the last quarter is steep climbing. Not much shadow and sometimes boring route. No water when you start climbing. Be prepared!
Up to the mountain the route is well signed. At the mountain less and less and often on the wrong side (look backwards). Then suddenly you go steep down on a small track. Bit difficult.
The town is small and nobody seems to speak English. The monastery is often closed and do not answer the bell. I was told a room is 9o- euro. An albergue (6 euro) and two bars with rooms (40 eruo) are nearby. No problem. No tienda or supermarket available!
The second stage begins beautiful. Lousy marking. I had to follow other signs and sometimes just guess.. At the first crossing without signs, stay on the right side. Do not cross the bridge. But the way is breathtaking.
Then you walk on towards Villanova. At the end you have to climb a bit before you reach sea for a swim!
In Villanova you can choose to go next day by boat to near-Padron (16,50 euro pp!), walk 28 km or -but i do not have details- take a train.
The boat trip is nice but the driver only speak Spanish. We were happy to have a pilgrim on board to translate.
All at all:
often beautiful
first day climbing for several hours without water
a bit commercial
peaceful (only 5 pilgrims took this route)
only Spanish
monastery not open
I would do it again!
